City University
London, United Kingdom
This talk presents a new model of concentration fluctuations for neutrally buoyant and dense gas clouds dispersing in a wind-tunnel. It is derived from a series of exact results which apply in the hypothetical case when there is no molecular diffusion, coupled with a pdf model previously used to describe steady releases of contaminant. A simple relationship between the evolution of the concentration intensity and mean is established. Preliminary experimental evidence for neutrally buoyant releases suggests the relationship is self similar. The basic model is extended, by means of a perturbation term, to describe the distinctive features exhibited by dense gas clouds. The implications for modelling higher moments of concentration and the fixed point pdf are discussed.